Lightweight valves of the kind referred to here are known (DE 198 04 053 A1). They are used inter alia as inlet and outlet valves for internal combustion engines and comprise a solid or hollow valve stem, a funnel/trumpet-shaped valve cone and a valve disk. For the purpose of weight reduction, the valve cone is hollow and therefore has only a small wall thickness. The valve cone is designed either in one piece with the valve stem or the valve disk or as a separate component which is welded to the valve stem and the valve disk.
As the valve disk is not supported on a large area owing to the hollow space in the valve cone and the valve cone moreover has only a small wall thickness, the valve disk may be deformed during operation by the combustion pressure in the combustion chamber of the internal combustion engine, which contributes to premature wear of the lightweight valve. Furthermore, the thin-walled valve cone may also be deformed. In order to prevent this, DE 198 04 053 A1 proposes making the valve stem so long that it bears with its end face against the valve disk on the flat side thereof facing away from the combustion chamber, by virtue of which the disk is supported. In this connection, the valve stem and the valve disk can be welded together in their contact region. In other embodiments, the valve disk is supported against the valve stem by means of an intermediate piece designed in one piece on the valve cone or a separate sleeve, fixed between valve stem and valve disk.
It is a disadvantage of the known lightweight valve that accurate relative alignment of the individual parts, in particular the valve stem and the valve disk, before the joining process can be brought about only with high outlay. While it is true that one illustrative embodiment (FIG. 3) of the known lightweight valve provides centering on the valve disk for the valve stem, slanting of the valve stem in relation to the valve disk while they are being welded together nevertheless cannot be excluded without accurate holding of valve stem and disk by means of appropriate devices.